| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package org.apache.flink.util; |
| |
| import org.apache.flink.annotation.Public; |
| import org.apache.flink.types.LongValue; |
| |
| import java.util.NoSuchElementException; |
| |
| /** |
| * The {@code LongValueSequenceIterator} is an iterator that returns a sequence of numbers (as |
| * {@code LongValue})s. The iterator is splittable (as defined by {@link SplittableIterator}, i.e., |
| * it can be divided into multiple iterators that each return a subsequence of the number sequence. |
| */ |
| @Public |
| public class LongValueSequenceIterator extends SplittableIterator<LongValue> { |
| |
| private static final long serialVersionUID = 1L; |
| |
| /** The last number returned by the iterator. */ |
| private final long to; |
| |
| /** The next number to be returned. */ |
| private long current; |
| |
| /** The next value to be returned. */ |
| private LongValue currentValue = new LongValue(); |
| |
| /** |
| * Creates a new splittable iterator, returning the range [from, to]. Both boundaries of the |
| * interval are inclusive. |
| * |
| * @param from The first number returned by the iterator. |
| * @param to The last number returned by the iterator. |
| */ |
| public LongValueSequenceIterator(long from, long to) { |
| if (from > to) { |
| throw new IllegalArgumentException( |
| "The 'to' value must not be smaller than the 'from' value."); |
| } |
| |
| this.current = from; |
| this.to = to; |
| } |
| |
| /** |
| * Internal constructor to allow for empty iterators. |
| * |
| * @param from The first number returned by the iterator. |
| * @param to The last number returned by the iterator. |
| * @param unused A dummy parameter to disambiguate the constructor. |
| */ |
| private LongValueSequenceIterator(long from, long to, boolean unused) { |
| this.current = from; |
| this.to = to; |
| } |
| |
| public long getCurrent() { |
| return this.current; |
| } |
| |
| public long getTo() { |
| return this.to; |
| } |
| |
| @Override |
| public boolean hasNext() { |
| return current <= to; |
| } |
| |
| @Override |
| public LongValue next() { |
| if (current <= to) { |
| currentValue.setValue(current++); |
| return currentValue; |
| } else { |
| throw new NoSuchElementException(); |
| } |
| } |
| |
| @Override |
| public void remove() { |
| throw new UnsupportedOperationException(); |
| } |
| |
| @Override |
| public LongValueSequenceIterator[] split(int numPartitions) { |
| if (numPartitions < 1) { |
| throw new IllegalArgumentException("The number of partitions must be at least 1."); |
| } |
| |
| if (numPartitions == 1) { |
| return new LongValueSequenceIterator[] {new LongValueSequenceIterator(current, to)}; |
| } |
| |
| // here, numPartitions >= 2 !!! |
| |
| long elementsPerSplit; |
| |
| if (to - current + 1 >= 0) { |
| elementsPerSplit = (to - current + 1) / numPartitions; |
| } else { |
| // long overflow of the range. |
| // we compute based on half the distance, to prevent the overflow. |
| // in most cases it holds that: current < 0 and to > 0, except for: to == 0 and current |
| // == Long.MIN_VALUE |
| // the later needs a special case |
| final long halfDiff; // must be positive |
| |
| if (current == Long.MIN_VALUE) { |
| // this means to >= 0 |
| halfDiff = (Long.MAX_VALUE / 2 + 1) + to / 2; |
| } else { |
| long posFrom = -current; |
| if (posFrom > to) { |
| halfDiff = to + ((posFrom - to) / 2); |
| } else { |
| halfDiff = posFrom + ((to - posFrom) / 2); |
| } |
| } |
| elementsPerSplit = halfDiff / numPartitions * 2; |
| } |
| |
| if (elementsPerSplit < Long.MAX_VALUE) { |
| // figure out how many get one in addition |
| long numWithExtra = -(elementsPerSplit * numPartitions) + to - current + 1; |
| |
| // based on rounding errors, we may have lost one) |
| if (numWithExtra > numPartitions) { |
| elementsPerSplit++; |
| numWithExtra -= numPartitions; |
| |
| if (numWithExtra > numPartitions) { |
| throw new RuntimeException("Bug in splitting logic. To much rounding loss."); |
| } |
| } |
| |
| LongValueSequenceIterator[] iters = new LongValueSequenceIterator[numPartitions]; |
| long curr = current; |
| int i = 0; |
| for (; i < numWithExtra; i++) { |
| long next = curr + elementsPerSplit + 1; |
| iters[i] = new LongValueSequenceIterator(curr, next - 1); |
| curr = next; |
| } |
| for (; i < numPartitions; i++) { |
| long next = curr + elementsPerSplit; |
| iters[i] = new LongValueSequenceIterator(curr, next - 1, true); |
| curr = next; |
| } |
| |
| return iters; |
| } else { |
| // this can only be the case when there are two partitions |
| if (numPartitions != 2) { |
| throw new RuntimeException("Bug in splitting logic."); |
| } |
| |
| return new LongValueSequenceIterator[] { |
| new LongValueSequenceIterator(current, current + elementsPerSplit), |
| new LongValueSequenceIterator(current + elementsPerSplit, to) |
| }; |
| } |
| } |
| |
| @Override |
| public int getMaximumNumberOfSplits() { |
| if (to >= Integer.MAX_VALUE |
| || current <= Integer.MIN_VALUE |
| || to - current + 1 >= Integer.MAX_VALUE) { |
| return Integer.MAX_VALUE; |
| } else { |
| return (int) (to - current + 1); |
| } |
| } |
| } |